1. Field of the Invention
The present invention relates to a gas separating material. More particularly, the present invention relates to a gas separating material useful for separating a mixed gas consisting of a plurality of component gases, for example, carbon dioxide gas and methane gas or carbon dioxide gas and nitrogen gas, into the component gases, or for concentrating a specific component gas from the mixed gas.
2. Description of the Related Art
It is known that various aromatic imide polymer membranes are usable as a gas separating material. For example, Japanese Unexamined Patent Publication (Kokai) No. 57-15819 and U.S. Pat. No. 4,378,400 disclose gas separating material having a gas-separating layer consisting of an aromatic imide polymer derived from a biphenyl tetracarboxylic acid and an aromatic diamine, for example, diaminodiphenylether, diaminodiphenyl thioether, diaminodiphenyl methane, or diaminobenzophenone.
However, it is also known that conventional gas separating materials having the aromatic imide polymer layer exhibit a low permeability coefficient of carbon dioxide gas and therefore, are unsatisfactory for separating or concentrating carbon dioxide gas from the mixture gas containing carbon dioxide gas.
Generally, aromatic imide polymer has an excellent heat-resisting property, a superior chemicalresisting property, and satisfactory mechanical properties. Accordingly, it is strongly desired by industry to provide an aromatic imide polymer gas separating material useful for separating and concentrating carbon dioxide gas.